Enhancement and Switching of Fano Resonance in Metamaterial

Excitation and manipulation of Fano resonances in plasmonic nanostructure have attracted considerable attention due to its capability of degrees of freedom in artificial design especially for spectral positions and quality factors (Q factors). To utilize the high Q factor of Fano resonances in practical applications, their sharp peaks or dips should be well detected, which means a high intensity of resonance line shape. Thus far, the realization of Fano resonant nanostructure with both the high Q factor and the intensity to overcome the trade-off between them remains a challenge. This study both numerically and experimentally demonstrates that the high Q factor and Fano intensity are simultaneously sustained in near-infrared region. A Fano metamaterial consisting of gold double nanorods and film with dielectric spacer between them to enhance the Fano resonance is proposed. Due to their strong near-field coupling, the performance of the Fano resonance is significantly improved and the intensities of in-phase and out-of-phase plasmonic resonances can be flexibly manipulated by easily changing the angle of incident light. These results show a novel approach with important implications of Fano resonances for realizing practical applications in optical sensing including chemical or biomedical sensors, enhanced spectroscopy, and nonlinear optical devices.